The processes involved in subgroup formation and maintenance were studied in a captive colony of squirrel monkeys (Saimiri sciureus) containing 2 adult males, 6 adult females, 2 infant males, and 1 juvenile male. On two successive occasions, the group was divided in half, placing an adult female from one subgroup with members of the other major subgroup. In both cases the experimental female was not admitted to the adult female huddle group but was accepted into a huddle group with the adult and juvenile males. Grouping tendencies during the 5 weeks of testing are described in terms of spatial cliques, and behavioral interactions are analyzed to identify the processes responsible for subgroup patterns in squirrel monkeys.